Dates

For more accuracy use, window.performance.now()

Date() // => "Tue Jan 21 2020 23:50:09 GMT-0800 (Pacific Standard Time)"
let x = new Date() //create Date object
x.toDateString(); //=> "Tue Jan 21 2020"
x.toISOString(); //=> "2018-12-31T03:21:15.934Z"
x.toGMTString(); //=> "Wed, 22 Jan 2020 07:48:33 GMT"
x.toLocaleDateString(); //=> "1/21/2020"

Parsing dates with new Date() varies across browsers, recommended against

DateFns

npm install date-fns

Better than moment b/c selective importing and uses normal js date object

< and > works on Date objects but not == or ===

import { format, compareAsc } from 'date-fns'

// Add any duration to 1 September 2014, 10:19:50
const result = add(new Date(2014, 8, 1, 10, 19, 50), {
  years: 2,
  months: 24,
  days: 7,
  hours: 5,
  minutes: 9,
  seconds: 30,
})

Formatting

import { format, formatDistance, formatRelative, subDays } from 'date-fns'

format(new Date(), "'Today is a' iiii")
//=> "Today is a Thursday"

formatDistance(subDays(new Date(), 3), new Date())
//=> "3 days ago"

formatRelative(subDays(new Date(), 3), new Date())
//=> "last Friday at 7:26 p.m."

Formatting Strings

Unit	Pattern	Result examples	Notes
Era	G..GGG	AD, BC
	GGGG	Anno Domini, Before Christ	2
	GGGGG	A, B
Calendar year	y	44, 1, 1900, 2017	5
	yo	44th, 1st, 0th, 17th	5,7
	yy	44, 01, 00, 17	5
	yyy	044, 001, 1900, 2017	5
	yyyy	0044, 0001, 1900, 2017	5
	yyyyy	...	3,5
Local week-numbering year	Y	44, 1, 1900, 2017	5
	Yo	44th, 1st, 1900th, 2017th	5,7
	YY	44, 01, 00, 17	5,8
	YYY	044, 001, 1900, 2017	5
	YYYY	0044, 0001, 1900, 2017	5,8
	YYYYY	...	3,5
ISO week-numbering year	R	-43, 0, 1, 1900, 2017	5,7
	RR	-43, 00, 01, 1900, 2017	5,7
	RRR	-043, 000, 001, 1900, 2017	5,7
	RRRR	-0043, 0000, 0001, 1900, 2017	5,7
	RRRRR	...	3,5,7
Extended year	u	-43, 0, 1, 1900, 2017	5
	uu	-43, 01, 1900, 2017	5
	uuu	-043, 001, 1900, 2017	5
	uuuu	-0043, 0001, 1900, 2017	5
	uuuuu	...	3,5
Quarter (formatting)	Q	1, 2, 3, 4
	Qo	1st, 2nd, 3rd, 4th	7
	QQ	01, 02, 03, 04
	QQQ	Q1, Q2, Q3, Q4
	QQQQ	1st quarter, 2nd quarter, ...	2
	QQQQQ	1, 2, 3, 4	4
Quarter (stand-alone)	q	1, 2, 3, 4
	qo	1st, 2nd, 3rd, 4th	7
	qq	01, 02, 03, 04
	qqq	Q1, Q2, Q3, Q4
	qqqq	1st quarter, 2nd quarter, ...	2
	qqqqq	1, 2, 3, 4	4
Month (formatting)	M	1, 2, ..., 12
	Mo	1st, 2nd, ..., 12th	7
	MM	01, 02, ..., 12
	MMM	Jan, Feb, ..., Dec
	MMMM	January, February, ..., December	2
	MMMMM	J, F, ..., D
Month (stand-alone)	L	1, 2, ..., 12
	Lo	1st, 2nd, ..., 12th	7
	LL	01, 02, ..., 12
	LLL	Jan, Feb, ..., Dec
	LLLL	January, February, ..., December	2
	LLLLL	J, F, ..., D
Local week of year	w	1, 2, ..., 53
	wo	1st, 2nd, ..., 53th	7
	ww	01, 02, ..., 53
ISO week of year	I	1, 2, ..., 53	7
	Io	1st, 2nd, ..., 53th	7
	II	01, 02, ..., 53	7
Day of month	d	1, 2, ..., 31
	do	1st, 2nd, ..., 31st	7
	dd	01, 02, ..., 31
Day of year	D	1, 2, ..., 365, 366	9
	Do	1st, 2nd, ..., 365th, 366th	7
	DD	01, 02, ..., 365, 366	9
	DDD	001, 002, ..., 365, 366
	DDDD	...	3
Day of week (formatting)	E..EEE	Mon, Tue, Wed, ..., Sun
	EEEE	Monday, Tuesday, ..., Sunday	2
	EEEEE	M, T, W, T, F, S, S
	EEEEEE	Mo, Tu, We, Th, Fr, Su, Sa
ISO day of week (formatting)	i	1, 2, 3, ..., 7	7
	io	1st, 2nd, ..., 7th	7
	ii	01, 02, ..., 07	7
	iii	Mon, Tue, Wed, ..., Sun	7
	iiii	Monday, Tuesday, ..., Sunday	2,7
	iiiii	M, T, W, T, F, S, S	7
	iiiiii	Mo, Tu, We, Th, Fr, Su, Sa	7
Local day of week (formatting)	e	2, 3, 4, ..., 1
	eo	2nd, 3rd, ..., 1st	7
	ee	02, 03, ..., 01
	eee	Mon, Tue, Wed, ..., Sun
	eeee	Monday, Tuesday, ..., Sunday	2
	eeeee	M, T, W, T, F, S, S
	eeeeee	Mo, Tu, We, Th, Fr, Su, Sa
Local day of week (stand-alone)	c	2, 3, 4, ..., 1
	co	2nd, 3rd, ..., 1st	7
	cc	02, 03, ..., 01
	ccc	Mon, Tue, Wed, ..., Sun
	cccc	Monday, Tuesday, ..., Sunday	2
	ccccc	M, T, W, T, F, S, S
	cccccc	Mo, Tu, We, Th, Fr, Su, Sa
AM, PM	a..aa	AM, PM
	aaa	am, pm
	aaaa	a.m., p.m.	2
	aaaaa	a, p
AM, PM, noon, midnight	b..bb	AM, PM, noon, midnight
	bbb	am, pm, noon, midnight
	bbbb	a.m., p.m., noon, midnight	2
	bbbbb	a, p, n, mi
Flexible day period	B..BBB	at night, in the morning, ...
	BBBB	at night, in the morning, ...	2
	BBBBB	at night, in the morning, ...
Hour [1-12]	h	1, 2, ..., 11, 12
	ho	1st, 2nd, ..., 11th, 12th	7
	hh	01, 02, ..., 11, 12
Hour [0-23]	H	0, 1, 2, ..., 23
	Ho	0th, 1st, 2nd, ..., 23rd	7
	HH	00, 01, 02, ..., 23
Hour [0-11]	K	1, 2, ..., 11, 0
	Ko	1st, 2nd, ..., 11th, 0th	7
	KK	01, 02, ..., 11, 00
Hour [1-24]	k	24, 1, 2, ..., 23
	ko	24th, 1st, 2nd, ..., 23rd	7
	kk	24, 01, 02, ..., 23
Minute	m	0, 1, ..., 59
	mo	0th, 1st, ..., 59th	7
	mm	00, 01, ..., 59
Second	s	0, 1, ..., 59
	so	0th, 1st, ..., 59th	7
	ss	00, 01, ..., 59
Fraction of second	S	0, 1, ..., 9
	SS	00, 01, ..., 99
	SSS	000, 001, ..., 999
	SSSS	...	3
Timezone (ISO-8601 w/ Z)	X	-08, +0530, Z
	XX	-0800, +0530, Z
	XXX	-08:00, +05:30, Z
	XXXX	-0800, +0530, Z, +123456	2
	XXXXX	-08:00, +05:30, Z, +12:34:56
Timezone (ISO-8601 w/o Z)	x	-08, +0530, +00
	xx	-0800, +0530, +0000
	xxx	-08:00, +05:30, +00:00	2
	xxxx	-0800, +0530, +0000, +123456
	xxxxx	-08:00, +05:30, +00:00, +12:34:56
Timezone (GMT)	O...OOO	GMT-8, GMT+5:30, GMT+0
	OOOO	GMT-08:00, GMT+05:30, GMT+00:00	2
Timezone (specific non-locat.)	z...zzz	GMT-8, GMT+5:30, GMT+0	6
	zzzz	GMT-08:00, GMT+05:30, GMT+00:00	2,6
Seconds timestamp	t	512969520	7
	tt	...	3,7
Milliseconds timestamp	T	512969520900	7
	TT	...	3,7
Long localized date	P	04/29/1453	7
	PP	Apr 29, 1453	7
	PPP	April 29th, 1453	7
	PPPP	Friday, April 29th, 1453	2,7
Long localized time	p	12:00 AM	7
	pp	12:00:00 AM	7
	ppp	12:00:00 AM GMT+2	7
	pppp	12:00:00 AM GMT+02:00	2,7
Combination of date and time	Pp	04/29/1453, 12:00 AM	7
	PPpp	Apr 29, 1453, 12:00:00 AM	7
	PPPppp	April 29th, 1453 at ...	7
	PPPPpppp	Friday, April 29th, 1453 at ...	2,7

Moment.js (Similar to Dayjs)

Creation

moment(String);
moment("12-25-1995", "MM-DD-YYYY"); //pass format of string 

Formatting

//This one is the best because string sorting works
moment().format(); // 2019-04-28T23:22:28-07:00

moment().format('MMMM Do YYYY, h:mm:ss a'); 
// April 28th 2019, 11:22:28 pm
moment().format('dddd'); // Sunday
moment().format("MMM Do YY"); // Apr 28th 19
moment().format('YYYY [escaped] YYYY');     
// 2019 escaped 2019

Operations

let today = moment();
today.add(config.add_days, 'days');
today.subtract(1, "days");

Get And Setters

Leave empty to get and give Number/String to set

moment().month();//return 0-11 which is Jan-Dec
moment().day();//return 0-6 which is Sun-Sat
moment().date(); //return 1-31 for day of month

Operations

moment('2016-10-30').isBetween('2016-10-30', '2016-12-30', null, '()'); //false
moment('2016-10-30').isBetween('2016-10-30', '2016-12-30', null, '[)'); //true

Plugins

moment-business-days

Only work with business days adding fts like isHoliday and businessDiff to moment